Experimentation has shown that a weakly driven output driver circuit can be susceptible to pulsed radar and other electromagnetic interference (EMI) noise sources. Transients from EMI sources can cause a weakly driven output driver to change state, resulting in false output pulses or no output at all. On the other hand, driving an output driver too strongly can cause a burst of current to occur during switching that can create a radiated emission problem. In this scenario, the strongly driven output driver can actually act as a source of EMI to other nearby electronic devices or itself.
One technique that has been used to reduce the possibility that an output driver will radiate in an undesired manner is to adjust the fall time of the output signal generated by the driver. However, the fall time is typically adjusted by reducing the drive level of the driver, which increases the susceptibility of the circuit to EMI. Techniques and circuits are needed that will allow an output driver to have a reduced likelihood of generating undesired emissions, while having enhanced immunity to EMI and other noise sources.